With an increase in the density of LSI, the circuit line width of semiconductor devices has decreased through the years. To form a desired circuit pattern for such semiconductor devices, an original image pattern (i.e., a mask or, particularly, a reticle for use in steppers or scanners) with high precision formed on quartz is transferred onto a wafer with its size reduced by using reduction projection light-exposure apparatus. The original image pattern with high precision is written by an electron beam writing apparatus, i.e., with a so-called electron beam lithography technique.
Known electron beam writing apparatuses are a variable shaped electron beam writing apparatus and a multi-beam writing apparatus. The variable shaped electron beam writing apparatus forms an electron beam into a rectangle or an isosceles right triangle by using two shaping apertures, and applies an electron beam on a mask as a writing object. On the other hand, the multi-beam writing apparatus causes an electron beam emitted from an electron gun to pass through an aperture member with a plurality of holes to form multi-beams. Each of the beams is blanking-controlled. The beams which have not been blocked are applied onto a mask as a writing target.
In the case of performing electron beam writing with a variable shaped electron beam writing apparatus, a layout of a semiconductor integrated circuit is first designed, and design data (CAD data) is generated as layout data. Then, the format of the design data is converted such that the converted data can be processed in the writing apparatus, and writing data is generated. For example, in the writing data, a writing pattern such as a graphic is defined by coordinates of vertices of the graphic.
The design data and the writing data are vector data. In a conventional technique, to check matching in shape between data before data conversion and data after the data conversion, an exclusive OR (XOR) operation is performed on the design data and the writing data, and a difference is detected as a defect (conversion error).
In the case of performing electron beam writing with a multi-beam writing apparatus, the format of design data is converted so that vector writing data is generated, and then the vector writing data is converted to pixel writing data, and the pixel writing data is input to the writing apparatus.
In detecting the presence of an conversion error occurring when vector writing data is converted to pixel writing data, vector data and pixel data are used for comparison. Thus, the conventional technique described above cannot be applied without change.